Extractive distillation of normal primary alcohols



May 8, 1951 c. s. CARLSON ETAL EXTRACTIVE DISTILLATION OF NORMAL PRIMARY ALCOHOLS '7 Sheets-Sheet l Filed June 24, 1948 b5 W w( clbbone EXTRACTIVE DISTILLATION OF NORMAL PRIMARY ALCOHOLS Filed June 24, 1948 May 8, 1951 c. s. CARLSON ETAL '7 Sheecs--Shee'cI 2 23S Mw? @M Clt/t, ormegc. s. CARLSON ETAL May 8, 1951 7 Sheets-Sheet 3 Filed June 24, 1948 .awk/2 N I 0 2 s F O OH ON O@ Ov. Om O@ Ob O@ Om OOMU m au@ n I.. A@ L n l i w m f2 M Hw b J G mo Z lg vw mies@ E n J N d om M M GmL 6 n 265m Il DN S Y U H h 1% @.b G. Ecc? n 1o N02 IOE |C l a 1o No 102416 l z w m 103.@ No2 mw Ionmndl 2 .f ON JOIOUJ 103mm@ No mw IODQIC l J AA 102mb No2 IODQ; m In ,Af 105-@ wo Q 102m; @s H m -5U May 8, 1951 c. s. CARLSON ETAL EXTRACTIVE DISTILLATION OF NORMAL PRIMARY ALCUHOLS 7 Sheets-Sheet 4 Filed June 24, 1948 NQ ON l 951.84... ULL

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EXTRACTIVE DISTILLATION OF NORMAL PRIMARY ALCOHOLS Filed June 24, 1948 7 Sheef,s-Shee'cI 6 Low- BOILING rz-C3 RANGE IMPURITIES rz- C4* [(101 212P 225 1 i4 H20 fafa@ AL 211 :fi-gigi.; "OO NTRAnNER '2O l QZ'lf 1 T AQ-I2C4+ RANGE r nC4+ RANGE OIL BR. C413 LEGEND n. NORMAL ALCOHOL. r3'2- "(255 BR BRANCHED ALCOHOL AQ AQUEoUs i OIL PAI G 6 Carl 5, Carlson E35 0h/1;( @M Clbborne May 8, 1951 c. s. CARLSON ETAL 2,551,584

EXTRACTIVE DISTILLATION OF' NORMAL PRIMARY ALCOHOLS Filed June 24, 1948 '7 Sheets-Sheet 7 mmnnlu am N enrich- Mwmlz Gom Q o H E,

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wDOmDGQ GQ ulOwEOmNQ u 10 mE a mmm UQ e n F O w M/ U@ b .Patentedv May 8, 195i Y A i '2,551,584 EXTRACTI'VE DIsfriLLATIoN. oF NORML" PRIMARY LCOHOIiS Carl s. Carlson, Elizabeth, and oharllesli rell and Paul Y, Smith, J1'., We stiield, 4 N.

signos to Standard Oil Development Company, a corporation of Delaware Application June 24, 194s, serial Nb. 34,856

16 clims. (cl. 2oz-239.5)

This invention relates t a practicalr method of separating Wide-boiling mixtues of oxygenated organic compounds and more particularly relates tothe segregation of the normal primary' alcohols'from such a Wide'boli'ng mixture.

Wide-boiling mixtures ofI oxyg'eiiated organicv compounds may be obtained, for example by the Fischer synthesis" in which carbon monoxide is reacted with hydrogen to produce af mixture of hydrocarbons and oxygenated organic compounds which separate into 'an oil layer' and a'water layer,

both of which contain Various hydrocarbons, ketones, alde'hyde's, etheis, acetals, ketals,l esters, carboxylic acids, normal'prim'ary, branched chain primary, secondary and tertiary alcohols of a Wide range ofV molecular Weights. The process of the present invention is particularly adapted to the treatment oi the water layer from the Fischersyr'thesis but may also be' -a'pplied'to the oil layer and gas phases after an appropriate scrubbing procedure, e. g., using Water to separate the oxygenated compounds as a water solution. Still another source of these wideebolllng mixtu'res of oxygenated organic compounds is inthe products of hydrocarbon oxidation rwhere `both oil and water layers are obtained, each of which conL tains oxygenated organic' compounds'. Aj typical example of the composition of the'y Water layer obtaineclin the Fischer process is as ioillowsi Azeotrope aai Pt o C Bolling f Pt., C.

Water (90.1 Wt. Per cent) 64. 7Y none 78. 5 78.1 82.3 80.4 82.8 79. 9 97.2 87. 7 99. 5 87. 5, 107.3 89.9 normal biity1 117. 7 92.2 normal amyl. 138 95.8 secondary amyl 119:94 92.3 tertiary amyl. 102. 4 87.2 iso am 131.6 95. 2 A1dehydes (1.0 wt. Per cent): y

acetaldehyde. 20. 2 none propionaldehyde. 48. 8 none n-butyraldehyde 75. 7 68Y normal 'valeraldchyde 103.7 80.6 isovaleraldehyde. 92. 5 82 Ketones (0.6 Wt. Per ce acetone; 56. 1 none methyl ethyl ketone 79. 6 73. 6 methyl propyl ketone. 102. 3 82. 9 methyl isopropyl'ketone;. 94. 3 methyl normal butyl ketone... 127,8 methyl isobutyl ketone 116; 0 87. 9 diethyl ketone 102l0 Esters (0.1 Wt. Per cent):

ethyl acetate L 77.2 70.4 normal propyl acetate 101; 6 82. 4 ethyl propl'onate 99.1 81.2 Acids (4.5 Wt. Per cent):

acetict.; 118' none propione. butyre valerio. Hydrocarbons@ ce) Ethers (trace) Ketals (trace) Acetals (t1 ace) 2 'Iyheseparatijonoff `the" normal primary alcoholsj from. Such; a. complex mixture. isi. dif. "lttj complish and1cannotkie done entirely by ordinary ds'llatin' b'auei the? fact' that' many ,fthej compounds boil' AWitliin very narrow rag'rigfels'v or form Vaqueousazeotrope-s boiling close together. Ilf'l addition; thelalcohl folfm lz'lrope'sj L other Oxy compoundsliwithand.Without Water as' a component, thus further'complcating the sepa. ration- Ifjthe crude aqueous inixt res of thealf lo11s} are 'subjected' tor'dinary fractihatiorifit is quite". feasible' to obtain narrow cutswhicii contain' the' followingv4 typesjoi'alco'liol mixvtnresglaltho 'gli inf practical separations alcoli' lf iorri'ol'legr paie" generally found in the; pli. d ie; and .$1,161. editie; groups due 'tothe nfllcy' of the flyati'ting system:

Narrowzboilinyfaneef mim-raadalcoholic".

l Normal Aqvileous;` Components B.1 Azeotrope C. ;.B.P.,C.

.A {meliaiiol am... Groupl ethano 1 78.-3 7.8..1 isopropanol 82. 4 80.2 nolymal prlopanol ,i Y isr u no Gloup um sendarybntan 99.5 3 88.5 tertiary p'et'anol 101:8. 8?.:0 ruormalbuianql. 117,7 92.2l isopenfanol 131.6 95.2 Griip III. `secondrypentano1 119:2. 92:3y .normalpentanol. 137.9vv 95.0 `pentanol-S.' 1.15.4* 35 It'i V to" be noted?tirat'tli"ennemis lieti psf` olf the alcoholsfin the above' types"'offn:` a.r'rfo'` clit mixtures f havefbol'ingi' points" which. differ lessiv than 57g.. which fact makes diflicultjthe finX ther sparation 1057i ordinary fractionatio n 4o ir the narrow boilingrange iri'ix'tre isoiliy. a; binaryortertiarymixt of the'al'c'o'hols G e'rally,tliecriide`-mixtures` containY nio tvv'of of the' alcohols and other o xygenatedy organic compounds tlfl'a'tl interfere With'separ'at'i nb o1 di'n'ary fractioi'ation,` but these do n'ot i with the Ybasic operation of this invention ink isloiatirig the desired' principal aiolioi components ofthe mixtures'.` -lt has been previously;v pi" ops'efdf' to separate the normal primary alcohols'l'byfrst fraction 7 ing" the' water layerjl obtained -I`1Q .l 3he. 1F"s`chei"y synthesis inthe 'presenteer alargjquantlts?" f aqueous refluxto 'remove the 'nonvalc'ohlic yc stitu'ents" an'dfthen' toffractionate Vthl alco after Afirst''removing`tlfie'f biillr "`oi the"` vvater, i the prescribeY `of` largejj quantities oi j"aqueous' "re tofobtain' a bottomsj fra`ctioiji Whiclfc whellyi of Herma? .primary .alcohols fr; from SelQ; ,darin teiay' and 'b're'nchd Chain' primary alcohols:l However, this 'mthod'hag h raised; vantageiha irl... .maar Ceses .larger ar'wleil .0f thenormal ainyl and higher' noinialv alcohols are lost in the rejected fraction containing the secondary, tertiary and branched chain primary alcohols. Under some circumstances even the normal butyl alcohol may be lost.

According to this invention a separation is effected between normal primary alcohols and branched primary, secondary and tertiary alcohols by subjecting the same to fractional distillation to separate the mixture into fractions based on the boiling range of the normal primary alcohols present in the fractions, for example, into a fraction containing all compounds boiling in the range of normal primary alcoholshaving up to and including two carbon atoms per molecule and a fraction containing all compounds boiling in the range of normal primary alcohols having more thaan two carbon atoms, and then subjecting each fraction to extractive distillation employing water as the extractive distillation solvent to separate the branched alcohols present in each fraction from the normal primary alcohols.

In copending application Serial Number 34,897, led June 24, .1.948, there is described a process operated under conditions whereby separation between normal primary alcohols and branched primary, secondary and tertiary alcohols can be effected without preliminary fractionation of the feed stock. These conditions are two, namely, (1) that the alcohol mixture be predominantly ethanol and the other alcohols are present in relatively small quantities, and (2) that the amount of water in the internal reux be maintained within closely controlled limits from 83 to 93.5 mol per cent, preferably 86 to 91 mol per cent.

It is therefore the main object of this invention to provide a process wherein all of the normal primary alcohols are obtained free of the secondary, tertiary and branched chain primary alcohols.

This and other objects of this invention are accomplished by separating the aqueous mixture of normal and branched primary, secondary, and tertiary alcohols, either before or after separation of the non-alcoholic constituents, into two or more fractions and then distilling each of these fractions in the presence of large quantities of solvent so as to remove an overhead fraction genated compounds (if present) and water, only vbranched primary, secondary, and tertiary alcohols free of normal primary alcohols.

Certain preferred details of operation together with additional objects and advantages will be apparent, and the invention itself will be best understood by reference to the following speciication and to the accompanying drawings, wherein:

Figures 1, 2 and 3 are charts representing the volatilities of various alcohols relative to ethyl alcohol in aqueous solutions.

Figure 4 illustrates a iiow plan of a unit for obtaining separation of normal primary alcohols from branched primary, secondary and tertiary alcohols. lin the figure the designation Br-n-Cz range on line 2'7 designates branched alcohols boiling in the range o1 the normal primary alcohols having up to and including 2 carbon atoms per molecule; while the designation Br-n-Cs-lrange on line 48 means those branched alcohols boiling in the range o normal primary alcohols having 3 or more carbon atoms per molecule.

Figure 5 illustrates a now plan of a modification of Figure 4. The designation Br-n-Cz range on line 27 has the same meaning as indicated in Figure 4. The designation Br-n-Cs range" on line 109 means branched alcohols boiling in the range oi normal propanol; while the designation Br-n-Ci-{J on line 115 means branched alcohols boiling in the range of the normal primary alcohols having 4 and more carbon atoms per molecule.

Figure 6 illustrates a modied now plan ol a portion of Figures 4 and 5.

Figure l illustrates a now plan of another modification of the process shown in Figure 4.

The present invention is made possible by the discovery that when a mixture of oxygenated compounds, such as those mentioned above, is distilled in the presence of a suiliciently large volume of an aqueous reflux, the normal volatilities of the compounds are altered and many separations which are impossible by ordinary iractionation become possible in the presence of the excess water. However, when this principle is used to separate economically desirable normal primary alcohols from economically not-so-desirable branched primary, secondary and tertiary alcohols, in very wide-boiling mixtures, the vola- .ny of the normal primary alcohols aie so closely similaito those of some of the less desirable alcohols that complete segregation of the normal primary alcohols is diilicult, if not impossible, to achieve.

It has been found, by varying the concentration of water in the reiiux, that the volatilities of the various alcohols in wide-boiling mixtures can be shifted, but even with the use of the most desirable water concentration the segregation is not complete. This is evident from a study of the charts illustrated in Figures 1, 2 and 3. In these charts the volatilities of iso and normal propanol, secondary and normal butanol, and normal amyl alcohols are shown graphically relative to ethanol. The curves plot respectively the change in volatility of the given alcohol with change in the amount of Water in the liquid phase at the limiting values of zero and 100% concentration of the alcohols in ethanol. Thus the area between the curves represents the total possible range in volatility with respect to ethanol and water content for each of the alcohols shown. From Figure 1 it is evident that the volatilities of normal and isopropyl alcohols approach each other closely in the region between 99 mol percent water and ininite dilution and that separation between these two alcohols is most readily accomplished at water concentrations below 70 mol percent. Furthermore, the isopropanol curve shows that a reasonable volatility of this compound relative to ethanol can be obtained at 8G mol per cent water, increasing with increasing Water concentration, thus permitting separation between ethanol and isopropanol at concentrations of water above incl percent. From Figure 2 it is evident that the volatilties of secondary butanol and normal propanol relative to ethanol are almost identical over most of the range of water concentrations although sec-butanol shows much greater volatility variation with variation in alcohol composition. The curves also show that separation can be accomplished readily in the region between mol percent water and iniinite dilution. Figure 3 shows the volatilities of normal and secondary butyl alcohols and normal amyl alcohol relative to ethanol. From the areas of the curves given, it is evident that normal butyl alcohol cannot be separated from either normall amyl a1- cohol or secondary butyl alcohol excepty at extremely high water dilution above 97 mol percent. On the other hand, normal amyl alcohol cannot be separated from secondary butyl alcohol at these high water dilutions but recourse must be had to dilutions below 85 mol percent. It is obvious, therefore, that both normal butyl and normal amyl alcohol cannot be separated from secondary butyl alcohol in a single distillation. Instead normal butyl alcoholl wouldI be separated from normal amyl alcohol and secondary butyl alcohol at water concentrations above 97 mol percent and the normal amyl alcohol could then be separated from the secondary butyl alcohol at water concentrations below 85- mol percent. If normal propyl alcohol were present it would be separated along with the normal butyl alcohol at high water concentrations;

Ina wide-boiling mixture of alcohols, such as obtained in the Fischer synthesis, the two most diiicultly removable impurities (that is, alcohols other than the normal primary alcohols) are isopropanol and secondary butanol. These two alcohols have approximately the same volatilities relative to ethanol at a water concentration of 90 mol percent. Below this water concentration the volatility of secondary butanol approaches that of normal propanol very rapidly, being nearly identical with that for normal propanol at about 81 mol percent and lower water concentrations. Above 90 mol percent water the volatility of normal propanol increases rapidly, approaching that of isopropanol.

However, isopropanol and secondary butanol Alternatively, the invention may be practiced' by splitting, by ordinary fractional distillation, the oxygenated compounds into (l) those compounds boiling upto and including normal propanol, and (2) those boiling higher than no1'- mal propanol and then extractively distilling each of these fractions with water. Under some circumstances it may be desirable to make this split so that some normal propanolI is present in each of these fractions. This latter methodl of operating has the advantage that close control of the initial fractionation isv avoided;

As pointed out above, the fractions obtained by any one of the above methods are each extractively distilled with water. However, it may be desirable to extractively distill the (Z3-C5 alcohol fraction and particularly the C4-C5 alcon hol fractionV with a solvent such` as a liquid hydrocarbon oil which is non-reactive with the alcohols and is liquid at the distillation temperature and boils no lower than the highest boiling constituent to be separated. This method of operating is advantageous because of the very low solubility of the higher alcohols in water..

necessitating very high Water concentrations when using water as the solvent.

The amount of water in the reflux in each i-nstance must be maintained within narrow limits, depending upon the fraction being distilled in order to completely separate the undesired components and obtain pure normal primary alcohols; This is clear from a study of Figures 1, 2 and 3 as pointed out above. water required for the extractive distillation of each cut is set forth in the following table:

TABLE II Purification of primary normal alcohols H2O Concentration (Mol Perr Cent) Range in Extractivo Distillation Cut to be Purified (Boiling.7 range of primary/normal alcohol) Operable 1 Preferred Cr-Cg isopropanol minor constituent. above 65 above 80 sopropanol major constituent. above 80` above 90 i 3- ethanol major constituent above 84;, 889, n-propanol major constituent.. above 86 C3 .out alone 'above S6 above 90 Cg-C 5 vcut 86-95 88-91 Cr-Ccut above Water solubility limit,l above 98 mol per cent when n-bunmol lgenerally above 90 niol per predominates and above 99.2 mol percent. cent when n-pentanol predominates at atmospheric pressure 1 The operable Water concentration range for the purpose of this table is taken as that water concentration at which an alpha of at least 1.2 is realized between the key components. Although possible, it is noi economically feasible to separate between the components when the alpha is less than 1.2.

can easily be separated by ordinary distillation of the water azeotropes of the alcohols. Hence, if a feed mixture of alcohols containing these compounds is fractionated to separate the principal normal primary alcohols into separate cuts, the isopropanol will distill with the ethanol cut and the secondary butyl alcohol Will distill with the normal propanol cut.

Thus the advantages of the present invention may be accomplished by fractionating the feed mixture of oxygenated conmpounds from the Fischer synthesis into a methanol-ethanol fraction, yand a fraction containing all higher boiling alcohols. Each of these fractions is then distilled in the presence of aqueous reux of carefully controlled water concentration. It may be desirable in some cases to separate the higherboiling fracticn into a propanol fraction* and a` higher boiling fraction and extractively distill each of these` fractions in the` presence of .f the required amounts.

of water.

Aspointed out above it is desirable to provide some method of removing undesired non-alcoholic constituents from the alcohols. This ispreferably accomplished by means of an extrac tive distillation with water as described in copending application, Serial No. 794,589, filed December 30, 1947. This extractive distillation may be either before or after the ordinary distillation into separate cuts. rllhis preliminary extractive distillation to separate non-alcoholic constituents is carried out in the presence of a much Wider range of water concentrations than that used in the second step to separate the nore mal primary alcohols. Thus, the water concentration for separating non-alcoholic compounds from alcohols may be between 65 and 99 mol percent on each plate, preferably to 85 mol percent. When the crude mixture of oxygenated 75 distilled with Water in twoV stages, first to sepa- The amount of feed rate, reiiux ratio, etc., that all compounds more volatile Vthan the acids are removed loverhead. These include alcohols, ketones, aldehydes, esters, acetals, ketals, and any Vsmall amount of hydrocarbons or ethers present. 'These compounds are withdrawn through -line '6, leaving an aqueous vacid bottoms `which is Withdrawn through line 1. The overhead vvapors are passed through condenser 8 to a receiver 9. A `portion of the condensate collected in receiver 9 is returned to the top of column I as external reflux through line I0. 4The remaining portion of the distillate collected in .receiver 9 is withdrawn through line I I. This Amixture vis then introduced into the middle portion of `tower 2 Awhere `it is fractionated in the presence of a liquid stream of water introduced through lline I2. Conditions are maintained in tower 2 such as kto cause distillation of the alcohols in the presence of water on each plate. A sunicient amount .of water is Aadded through line I2 so that it is present to the extent of 65 to 99 mol percent on each plate, vpreferably 75 to 85 mol percent. fThus the overhead vapors from tower 2 consist of carbonyls, esters, acetals, light hydrocarbons (if present), small amounts Aof alcohols, and ethers. These are kwithdrawn through line I3, condensed in cooler I4 and collected in accumulator I5. Aportion of the material in receiver I5 is passed by line I6 "to the top of tower 2 as internal reflux. The 'remainder is withdrawn'through line I 1 for further separation, if desired.

When hydrocarbons are present in the vfeed to tower 2, heavy components thereof often do `not distill overhead but are removed as bottoms. These hydrocarbons easily yseparate out as a highly insoluble `phase and vcan be decanted before the bottoms are further processed.

The alcohols freed of `undesired materials are removed from the bottom Vof tower 2 through line I8 and are introduced into the middle portion of tower 3 where they are Afractionated to take overhead, through line I9, methanol, ethanol, 'isopropanol, t-butanol, and water.

This overhead is condensed in cooler 2-I and collected in accumulator 22 from which a portion is returned to tower 3 through line 23 as yreflux and the remainder passed by 'line '24 to the midpoint of tower 25 where it is subjected to fractionation in the presence of large quantities of water introduced through line 26. Conditions are maintained in tower 25 such as to cause vdistillation of the alcohols in the presence of water on each plate as described in connection with* tower 2. A suicient amount of water is added through line 26 so that it is present to the extent of more than 80 mol percent on each plate. Under these conditions the isopropyl alcohol and tertiary butanol are rendered most volatile and are removed through line 21 together with a small amount of water. The remaining aqueous mixture of methanol and ethanol is withdrawn from tower 25 through line 28 and introduced into the midsection of tower 29 where the alcohols are recovered from the bulk of the water, which is withdrawn through line 30 and passed to line 26 to be used as the aqueous reflux introduced into the top of tower 25. A mixture of methanol and the waterethanol azeotrope -is withdrawn overhead through line 3I and introduced into the `midsection of tower 32 from which anhydrous methanol is withdrawn overhead through line 33 and the ethanol-water azeotrope through line 34.

Returning again yto 'tower 3, the 'bottoms fraction containing normal propanol, normal, Secondary, and isobutanol and all higher boiling alcohols is withdrawn through line 20 and is introduced into the midsection of tower 4 where it is V'fractionated in the presence of large quantities of water introduced through line 41. Sufficient water is introduced through line 47 to maintain between 88 and l91 mol percent on each plate. The operation of this tower is similar in all respects to that of towers 2 and 25. By maintaining the volume of water within the limits given, all of the secondary butyl, isobutyl, secondary, tertiary-, isoamyl and higher alcohols will be withdrawn overhead through line ZIB and all of the normal propyl, normal butyl and normal amyl alcohols will remain as bottoms and be withdrawn as an aqueous solution through line 49. This aqueous solution of normal alcohols is passed into vtower 50 where it is separated from the rbulk of the water which is recycled through line 5I toline 41 and used as the aqueous reflux introduced to the top of tower 4. yThe normal alcohol-water azeotro-pes are removed from tower 58 through line 52 Vfrom which the normal alcohols are separated 'by known ldehydration means and normal distillation.

Returning now to tower 3 it is within the scope of this invention to operate tower 3 so that the valcohols 'are separated into an overhead fraction consisting of methanol, ethanol, isopropanol, normal propanol, isobutanol, secondary butanol and tertiary butanol, leaving a bottoms fraction consisting of normal butanol andv all higher boiling fractions. Each of these fractions is extractively distilled with the required amounts of water in towers 25 and 4 respectively as described above, except that in this modification an amount of water is introduced into tower 25 to maintain above 86 mol percent (preferably 88-95 mol percent) on each plate. In those cases in which the source of the alcohols is from the Fischer synthesis, ethanol will be the major constituent, in lwhich case itis even more preferable to maintain a water concentration between 90 and 94 mol percent on each plate. In tower 4, the water concentration must be maintained above 90 mol percent (preferably above 98 mol percent when normal butanol predominates and above 99.2 mol percent when normal pentanol predominates). The large amounts of water required by this fraction is due to the very low solubility of the butanols and pentanols in water. For this reason, it may be desirable to distill the fraction in the presence of a non-polar solvent such as white oil as described below vin connection with Figure 6.

Instead of fractionating the mixture of alcohols vin tower '3 so that all of the normal propanol goes overhead it may often be desirable to operate this tower less eiiiciently in which case some of the normal propanol may be withdrawn in the bottoms. In such a case, the lextractive distillation in tower 4 Amay be conducted with lesser amounts of water as was described above when all of the normal propanol was withdrawn in the bottoms, e. g. the water concentration on each plate may be between 86 and 95 mol percent and preferably between 88 and 91 mol percent.

In Figure 5 is illustrated a modification of the rst embodiment of the process of Figure 4 in which the bottoms from tower 3 are subjected to further normal fractionation to give an overhead fraction containing alcohols boiling in the range of normal propyl alcohol and a bottoms fraction containing all higher boiling alcohols than normal propyl alcohol. Referring, therefore, to this drawing the bottoms from tower 3 containing normal propanol, normal, secondary, and isobutanol and all higher boiling alcohols is removed through line 20 and passed to tower |22 where it is again fractionated to take overhead. all alcohols boiling within the range of normal propyl alcohol and to remove as bottoms all higher boiling alcohols. Each of the two fractions obtained in tower are subjected to fractional distillation in the presence of large quantities of water to effect separation between the normal primary alcohols on the one hand and the branched primary, secondary, and tertiary alcohols on the other. The normal propanol cut is drawn overhead through line |0| and the bottoms fraction containing normal butyl and higher alcohols is Withdrawn through line |52. rhe crerhead fraction withdrawn through line l0| consists of normal propanol, secondary butanol, isobutanol and tertiary amyl alcohol. This fraction is condensed in cooler |03 and collected in accumulator |04 from which a portion is returned through line |05 to the top of tower |06 as redux therein. The remainder is passed by line |95 to the midsection of tower |07 where it is subjected to distillation in the presence of large quantities of water introduced through line E23. Sunicient Water is introduced through line |08 to maintain above 90 mol percent on each plate. The operation of this tower is similar in all respects to that of towers 2, 4 and 25 of Figure e. By maintaining the volume of water within the limits given, all of the secondary butyl, isobutyl and tertiary amyl alcohols will be withdrawn overhead through line |09 and all of the normal propyl alcohol will remain as bottoms and be withdrawn as an aqueous solution through line ||0. This aqueous solution of normal propyl alcohol is passed into tower S i where it is separated from the bulk of the water which is recycled through line I2 to line |023 and used as the aqueous redux introduced at the ton of tower |01. The normal propanol-water azeotrope is removed from tower through line l |3 and dehydrated according to known means.

The bottoms fraction from tower |00 consisting of higher alcohols in aqueous solution is withdrawn through line |02 and passed to the midsection of tower ||4 where it is fractionally distilled in the presence of large ouantities of water introduced through line A sucient amount of water is added through line H1 so that it is present on each plate below the alcohol feed point to the extent of above 98 mol percent. The water concentration above the alcohol feed point will approach very closelv the water concentration below the alcohol feed point. By operating under these conditions all of the branched alcohols and secondary and tertiary alcohols are taken ofi overhead through line ||5 and all of the normal primary alcohols are withdrawn in aqueous solution through line I6. This aqueous solution of normal primary alcohols is introduced into the midsection of tower ||B where they are distilled to remove the bulk of the water. The aqueous azeotropes of the alcohols are removed through line I9 and passed to tower |25 to complete the removal of water. The water is removed from tower H8 by line and introduced into line |30 to be recycled to tower I4 as the aqueous reflux therein. The dehydration in tower is preferably carried o ut in known manner in the presence of an entramer, for example, isopropyl ether or other substance well known in the art capable of removing water. Accordingly, isopropyl ether is introduced to the top of column |25 through line p |26 and the azeotrope of isopropyl ether and,

12 water is removed overhead through line |27 and passed to decanter |28 where two layers are formed. The upper, or isopropyl ether-rich layer, is recycled to the column |25 through line |29. Substantially ether-free water is removed through line i353 and recycled to tower |2| as the aqueous reiiux added through line |22. The distillation is carried out continuously removing essentially in column |25 all of the water overhead from the column and withdrawing a substantially anhydrous mixture of alcohols from the bottom of tower |25. These alcohols are removed through line I3! and passed to tower |32 where normal butyl alcohol is removed overhead through line |33 and normal amyl and higher primary alcohols are removed as bottoms through line |34.

In Figure 6 is shown a modification of the process of treating the bottoms fraction from tower EEO in Figure 5. Referring therefore to Figure 6, the aqueous bottoms from tower |99 are passed by line to an intermediate point of tower 2id where they are distilled to separate the alcohols from the water. This may be accomplished in any manner known in the art, but is preferably carried out by distilling the alcohols in the presence of an entraining agent for the water, such as isopropyl ether or other substance well known in the art capable of removing water. Accordingly, isopropyl ether is introduced into the top or" column 2 l Q through line 2| and the azeotrope oi isopropyl ether and water is removed overhead through line 2|2 and passed to decanter 2|3 where two layers are formed. The upper, or isopropyl ether-rich layer is recycled to the column 2|0 through line 2id. rEhe distillation is carried out continuously removing essentially in column 2|0 all of the water overhead and withdrawing a substantially anhydrous mixture of alcohols from the bottom of tower 2li?. These alcohols are removed through line 2 5 and passed to an interme-v diate point or tower 22| where they are fractionally distilled in the presence of large quanti ties of a hydrocarbon oil such as a white oil boiling from 39o-522 F. A sufcient amount of oil is added through line 222 so that it is present on each plate to the extent of about -99 Volume percent, preferably about volume percent on each plate, above the alcohol feed point. Conditions are maintained on each plate of the tower such that the liquid mixtures of the alcohols are at their boiling points in the oil and are continuously being contacted with vapors boiled from the plates below. Because of the enhanced volatility of the normal primary alcohols in relation to other alcohols the vapors are relatively rich in the former and poor in the latter. By controlling the amount of alcohol reflux and consequently the reux ratio and the number of plates, the actual degree of separation may be varied until the desired product purity and recovery are obtained. Thus suitable temperature and reflux conditions are maintained in the tower so that the normal primary alcohols are taken oi overhead through line 223 and all of the branched alcohols and secondary and tertiary alcohols arc ticularly the next lower boiling alcohol, in this case normal propyl alcohol. Tower 22"! is operated so as to separate the normal butyl, normal amyl and higher normal alcohols from both residual oil and lower boiling alcohols. .Since these lower boiling alcohols accumulate in the top ol the column, the normal alcohols are vwithdrawn a few plates from the top of the column through line 229. The impurities are drawn off through line 230 and the residual oil is withdrawn through line 23. The normal primary alcohols withdrawn through line 229 may be easily separated by ordinary fractionation, if desired.

The bottoms from tower 22! are passed byline 224 to tower 232 where the branched primary, l

with the appropriate large quantites of water to Y' separate overhead the branched primary, seco-ndary and tertiary alcohols together with the nonalcoholic constitutents.

Referring therefore to Figure '7, a water-layer having the composition used in Figure 4 is introduced into tower 39| which operates in the same manner as tower l of Figure 4 to separate overhead the nonacid constituents of the feed from the bulk of the water. These acid-free compounds are introduced into the midsection of tower 303 which operates in the same manner as tower 3 of Figure Ll. In this tower distillation is carried out so as to take overhead methyl alcohol., ethyl alcohol, isopropyl alcohol, t-butanol, acetone, acetaldehyde, prcpionaldehyde, butyra'ldehyde, dimethyl acetal, methyl ethyl ketone, ethyl acetate, light hydrocarbons, and other oxygenated compounds distilling `in this temperature range.

This fraction is then passed to tower v3255 by line :i2/where it is distilled in the presence of 80 to 99 mol percent of water as described in connection with tower 25 of Figure 4 to take overhead through line 321 isopropyl alcohol, tertiary Ibutanol, acetone, acetaldehyde, propionaldehyde, butyraldehyde, dimethyl acetahmethyl ethyl ketone, ethyl acetate and hydrocarbons. Methyl alcohol, ethyl alcohol and water are removed through line 328, separated from the bulk of water in tower 329 and into the individual alcohols in tower 93?. as described in Figure 4 with respect to towers 29 and 32 respectively.

Returning to tower 333, material boiling above ethyl alcohol is withdrawn through line 329 and passed to tower 394 where it is fractionated to separate overhead a fraction containing normal propyl alcohol, iso and secondary butyl alcohol, tertiary amyl alcohol, secondary amyl alcohol, isopropyl acetate, diethyl acetal, methyl normal propyl ketone, methyl isopropyl ketone, diethyl ketone, ethyl propionate, valeraldehyde, isovaleraldehyde, light hydrocarbons, and other oxygenated compounds boiling in this temperature range. This material is passed by line 3335 vto tower 346 where it is distilled in the presence of Accord- 86 to 99 mol percent of Water .to separate overhead via line 343 iso and secondary .butyl alcohol, tertiary amyl alcohol, secondary amyl alcohol, isopropyl acetate, diethyl acetal., methyl normal propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, ethyl propionate, valeraldehyde, isovaleraldehyde and light hy-- drooarbons. An aqueous `solution of normal propyl alcohol is withdrawn through line 343 and separated from vthe buik of the water in tower 359 as described in connection with tower 5U of Figure 4.

Bottoms from tower 394, consisting of normal butyl alcohol, normal branched primary and secondary amyl alcohol and all other constituents boiling thereabove including aldehydes, ketones, esters, hydrocarbons, etc., is passed vby line 3M to tower 353 where it is distilled in the presence of 85-99, preferably 98 to 99 mol percent water .to separate overhead a fraction consisting of branched primary and secondary amyl alcohols, any aldehydes, ketones, esters, and 'hydrocarbons present and a bottoms fraction consisting Yof normal butyl, normal amyl and higher primary alcohols. This fraction is passed by line 355 to tower 36! where it is separated from the bulk of the water. The aqueous alcohols removed from tower 36% are passed by line 333 to tower k39d where they are dehydrated in the `presence of an entrainer such as isopropyl ether as described in connection with tower |25 of Figure 5. The dehydrated alcohols are then separated in tower 37! in the same manner as described in connection with tower` 32 to Figure 5.

The nature and objects of the present invention having been thus fully set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patent is:

l. A method of separating a wide boiling mixture of organic compounds including normal, primary, branched primary, secondary and tertiary alcohols boiling within the range of methanol through n-pentanol which comprises introducing said mixture into a first fractionation Zone, fractionating said mixture in said rst fractionating zone to obtain overhead a rst fraction consisting of all compounds boiling within the range of the normal primary alcohols having up to and including 2 carbon atoms per molecule and a bottoms product containing all compounds boiling within and above the range of the normal primary alcohols having 3 and more carbon atoms, fractionally distilling the fraction boiling within the range of the normal primary alcohols having up to and including 2 carbon atoms per molecule in the presence of at least 65 mol percent water, fraotionally distilling the fraction consisting of all compounds boiling within and above the range of the normal primary alcohols having 3 and more carbon atoms in the presence of between 86 and 95 mol percent water to completely separate the normal primary alcohol from the remaining compounds in each vof said fractions.

2. The process according to claim l in which the fraction boiling within the range of the normal primary alcohol having up to and including 2 carbon atoms per molecule is :fractionally distilled in the presence of at least 80 mol percent water, the fraction consisting of all compounds boiling within the range of the normal primary alcohols having .3 and more carbon atoms, `is iractionally distilled in the presence of between `88 75 and 91 mol percent water.

15 3. A method of separating a Wide boiling aqueous mixture of organic compounds including normal primary, branched primary, secondary and tertiary alcohols boiling Within the range y methanol through n-pentanol which comprises introducing said mixture into a first fractionation zone, fractionating said mixture to obtain overhead with Water a first fraction consisting of all compounds boiling Within the range of normal primary alcohols having up to and including 3 carbon atoms per molecule and a bottoms product containing all compounds boiling within the range of normal primary alcohols having i and more carbon atoms, ractionally distiliing the fraction boiling Within the range of the normal primary alcohols having up and including 3 carbon atoms per molecule in the presence of at least 86 mol percent Water c4.nd iractionally distilling the fraction consisting or" all compounds boiling within the range oi primary alcohols having Ll and more carbon atoms in the presence or" at least 90 mol percent Wate 4. The process according to 3 in which the fraction boiling Within the range of normal primary alcohols hav/mg up to and including 3 carbon atoms per molecule is iractionally tilled in the presence of P8 to 95 mol j r water and the fraction containing all the coinpounds boiling within the ra of the non .l primary alcohols having 4 and acre carbon at ms is fractionally distilled in the gresence or at least 98 mol percent water.

5. The method of separatng a Wide boiling aqueous mixture of organic compounds including normal primary, branched primary, secondary and tertiary alcohols, boiling Within the range o methanol through n-pentanol which coml introducing said mixture into a first tracti ora zone, fractionating said mixture in Caid n tionation Zone to obtain overhead with first fraction consisting of all compounds boiling within the range of the normal primary alcohols having up to and including 2 carbon atoms and a portion of the compounds boiling Within the range of normal propyl alcohol and the bottom fraction containing all compounds boiling range of the normal primary alcohols more carbon atoms and also containing portion or" the compounds boiling in the range of normal propyl alcohol not distilling overhead, fractionally distilling the fraction boiling within the range of normal primary alcohols having up to and including 2 carbon atoms per molecule and also containing normal propyl alcohol in the presence oi at least 86 mol percent water and fracn tionally distilling the fraction containing all the compounds boiling Within the ange of the normal primary alcohols having 4.- and more carbon atoms and also containing normal propyl alcohol in the presence of between 85 95 mol percent water.

6. The process according to claim 5 in which the fraction boiling Within the range of normal primary alcohols having up to and including 2 carbon atoms per molecule and including a portion of the compounds boiling Within the range of normal propyl alcohol is fractionally dis 'lied in the presence oi 8S to 95 mol percent water a; i the fraction containing all the compounds boiling Within the range of the normal primary alcohols having l and more carbon atoms and containing that portion of the compounds boiling within the range of normal propyl alcohol not distilling overhead is fractionally distilled in the presence of 88 to 91 mol percent water.

'7. A method of separating a Wide boiling mixture of organic compounds, including normal primary, branched primary, secondary and tertiary alcohols, acetals, esters, ethers, ketals, hydrocarbon, ketones, and aldeliydes, boiling within the range oi methanol through n-pentanol, which comprises introducing said organic mixture into a first fractionation zone, fractionating said mixture in said ractionating Zone to obtain overhead all compounds boiling Within the range ofthe normal alcohols having up to and including 3 carbon atoms and a bottoms fraction containing all the compounds boiling -within the range of the normal alcohols having Il and more carbon atoms, passing said overhead. fraction to an intermediate point of a second fractionation Zone and the bottoms fraction to an intermediate point of a third fractionation zone, introducing into the top of the said second fractionation zone a sufficient amount or" Water to maintain above 86 inol percent of water in the internal reux and introducing into the top of said third 'fractionation zone a suiicient amount of water to maintain above 90 mol percent of water in the internal reflux, removing overhead from each of said second and third fractionation zones the esters, ethers, hydrocarbons, acetals, ketones, ketals, aldehydes, branched p imary, secondary, and tertiary alcohols and removing from the bottom of said second and third fractionation zone aqueous solution of normal primary alcohols.

8. The process according to claim 'l in which the fraction boiling within the range of normal primary alcohols having up to and including 3 carbon atoms per molecule is fractionally disu tilled in the presence of 88 to 95 percent water and the fraction containing all the compounds boiling Within the range of the normal primary alcohols having 4 and more carbon atoms is fractionally distilled in the presence of at least 93 mol percent Water.

9. The method of separating a wide boilingr mixture of organic compoun `s including alcohols boiling within the range of methanol through n-pentanol comprif-:cs introducing said organic mixture i to a first fractionation zone, fractionating said ir'rture in said first fractionation zone to obtain overhead a first fraction consisting of all compounds boiling within the range of the normal primary alcohols having up to and including 2 carbon atoms per molecule and a bottoms product containing all compounds boiling within and above the range of the normal primary alcohols having 3 and more carbon atoms, passing said bottoms product to a second fractionation zone, fractionating bottoms product in said second fractionating Zone to obtain overhead a second fraction consisting of all compounds boiling Within the range of normal propyl alcohol and as a bottoms product a third fraction containing all the compounds boiling within the range of the normal primary alcohols having 4 and more carbon atoms, iractionally distillinz; said iirst fraction in the presence of at least 65 mol percent water, fractionally distilling said second fraction in the presence of at least S6 mol percent Water, and fractionally distilling said third fraction in the presence of at least 9G mol percent water to separate the normal primary alcohols in each fraction from the remaining compounds.

1G. The process according to claim 9 in which the rst fraction is distilled in the presence of at least mol percent Water, the second fraction in the presence of at least 90 mol percent Water, and

l? the third fraction in the presence of at least 9G mol percent water.

11. A method of separating a wide boiling aqueous mixture of organic compounds including normal primary, branched primary, secondary and tertiary alcohols boiling within the range of methanol through n-pentanol which comprises introducing said mixture into a first fractionation zone, fractionating said mixture in said first fractionation zone to obtain overhead with water a first fraction consisting of all compounds boiling within the range of the normal primary alcohols having up to and including two carbon atoms per molecule and a bottoms product containing all compounds boiling within the range of the normal primary alcohols having 3 and more carbon atoms, passing said bottoms product to a second fractionation zone, fractionating said bottoms product in said second fractionating Zone to obtain overhead a second fraction consisting of all compounds boiling within the range ci normal propyl alcohol and as a bottoms product a third fraction containing all the compounds boiling within the range of the normal primary alcohols having 4 and more carbon atoms, fractionally distilling the fraction boiling within the range of the normal primary alcohols having up to and including two carbon atoms per molecule in the presence of at least 65 mol percent water, fractionally distilling the fraction consisting of all compounds boiling within the range of normal propyl alcohol in the presence of at least 86 mol percent water and fractionally distilling the fraction containing all the compounds boiling within the range of the normal primary alcohols having 4 and more carbon atoms in the presence of at least 90 mol percent water.

12. A method of separating a wide boiling mixture of organic compounds including esters, ethers, hydrocarbons, ketones, aoetals, lietals, and aldehydes and also containing alcohols boiling within the range of methanol through n-pentanol which comprises introducing said mixture into a rst fractionating zone wherein vapors of said mixture ascend countercurrently to a liquid reflux of the mixture dissolved in 65-99 mol percent of water whereby the normal volatility relationships of the organic compounds are altered and the ethers, esters, hydrocarbons, ketones, acetals, and aldehydes are rendered more volatile than the alcohols, continually removing water and the esters, ethers, hydrocarbons, aldehydes, acetals, ketals and ketones overhead from the fractional distillation Zone, removing a dilute aqueous solution of alcohols as a bottoms product, introducing said bottoms product into a second fractionation zone, fractionating said mixture in said second fractionation Zone to obtain overhead a second fraction consisting of all compounds boiling Within the range of the normal primary alcohols having up to and including 2 carbon atoms per molecule and a bottoms product containing all compounds boiling Within the range of the normal primary alcohols having 3 and more carbon atoms per molecule, passing said bottoms product into a third fractionation zone, fractionating said bottoms product in said third fractionation zone to obtain overhead a third fraction, consisting of all compounds boiling within the range of normal propyl alcohol and as a bottoms product a fourth fraction containing all the compounds boiling within the range of the normal primary alcohols having 4 and more carbon l 8 atoms, fractionally distilling each of said second, third and fourth fractions in the presence of sufiiciently large quantities of aqueous reflux to completely separate the normal primary alcohol-s from the remaining alcohols.

13. A process according to claim 11 in which the fraction boiling' within the range of the normal primary alcohols having up to and including 2 carbon atoms per molecule is fractionally distilled in the presence of at least 8G mol percent water, the fraction consisting of all compounds boiling within the range of normal propyl alcohol is fractionally distilled in. the presence of at least 99 mol percent water and the fraction containing all the compounds` boiling within the range of the normal primary alcohols having 4 and more carbon atoms is fractionally distilled in the presence of at least 98 molpercent water.

14. Process according to claim 12 wherein the said second fraction is fractionally distilled in the presence of at least 65 mol percent water, said third fraction is fractionally distilled in the presence of at least 86 mol percent Water, and the said fourth fraction is distilled in the presence of at least 9() mol percent water.

15. Process according to claim l2 in which the said second fraction is fractionally distilled in the presence of at least mol percent Water, the said third fraction is fractionally distilled in the presence of at least 90 mol percent Water and the lsaid fourth fraction is fractionally distilled in the presence of at least 98 mol percent water.

1. A method of separating a wide boiling mix- 'ture of organic compound including normal primary, branched primary, secondary and tertiary alcohols boiling Within the range of methanol through n-pentanol which comprises introducing said mixture into a iirst fractionation zone, fractionating said mixture in said first fractionating zone to obtain overhead a rst fraction consisting of all compounds boiling within the range of the normal primary alcohols having up to and including 2 carbon atoms per molecule and a bottoms product containing all compounds boiling within and above the range of normal primary alcohols having 3 and more carbon atoms per molecule and iractionally distilling the fraction consisting of all compounds boiling Within and above the range of the normal primary alcohols having 3 and more carbon atoms in the presence of between 86-95 mol percent Water to completely separate the normal primary alcohols from the remaining compounds in the fraction.

CARL S. CARLSON. CHARLES E. MORRELL. PAUL V. SMITH, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 887,793 Guillaume May 19, 19018 2,162,963 McKittrick June 30, 1937 2,290,442 Metzl July 21, 1942 2,321,748 Hopkins et al June 15, 1943 2,360,861 Pierotti et al Oct. 24, 1944 2,365,912 Souders Dec, 26, 1944 OTHER REFERENCES Journal of Research of the National Bureau of Standards, vol. 27, pages 44-46. 

16. A METHOD OF SEPARATING A WIDE BOILING MIXTURE OF ORGANIC COMPOUND INCLUDING NORMAL PRIMARY, BRANCHED PRIMARY, SECONDARY AND TERTIARY ALCOHOLS BOILING WITHIN THE RANGE OF METHANOL THROUGH N-PENTANOL WHICH COMPRISES INTRODUCING SAID MIXTURE INTO A FIRST FRACTIONATION ZONE, FRACTIONATING SAID MIXTURE IN SAID FIRST FRACTIONATING ZONE TO OBTAIN OVERHEAD A FIRST FRACTION CONSISTING OF ALL COMPOUNDS BOILING WITHIN THE RANGE OF THE NORMAL PRIMARY ALCOHOLS HAVING UP TO AND INCLUDING 2 CARBON ATOMS PER MOLECULE AND A BOTTOMS PRODUCT CONTAINING ALL COMPOUNDS BOILING WITHIN AND ABOVE THE RANGE OF NORMAL PRIMARY ALCOHOLS HAVING 3 AND MORE CARBON ATOMS PER MOLECULE AND FRACTIONALLY DISTILLING THE FRACTION CONSISTING OF ALL COMPOUNDS BOILING WITHIN AND ABOVE THE RANGE OF THE NORMAL PRIMARY ALCOHOLS HAVING 3 AND MORE CARBON ATOMS IN THE PRESENCE OF BETWEEN 86-95 MOL PERCENT WATER TO COMPLETELY SEPARATE THE NORMAL PRIMARY ALCOHOLS FROM THE REMAINING COMPOUNDS IN THE FRACTION. 